Dr. Newberg has isolated and partially characterized a small fucosylated oligosaccharide that inhibits the diarrheagenic effect of the stabile toxin of E. coli in human milk and protects the suckling infant from gastrointestinal tract infections. LSIMS, LSIMS/MS and the more sensitive MALDI-PSD-TOFMS will be used for structural determinations of the oligosaccharides.